(1) Field of the Invention
This invention relates to a catheter assembly and method for guiding a tip of a catheter within a blood vessel to an objective position.
(2) Description of the Prior Art
Recently, central venous catheters have been widely used for the purposes of hyperalimentation, measurement of central venous pressure, administration of chemotherapeutic, pressor, and vasopressor drugs, and emergency securing of an intravenous delivery route. Further, when inserting a catheter into a central blood vessel, the percutaneous catheterization method using a cannula made of plastic has been generally employed in place of the more conventional cut down method.
In the venipuncture for the percutaneous catherization method, the injective routes are cephalic vein, median cubital vein, internal jugular vein, subclavian vein, or external jugular vein.
When using the internal jugular vein as the insertion route, it is difficult to insert the catheter, and higher incidence of serious complications, such as carotid arterial injection, fistula of thoracic duct, hemothorax, or pneumothorax may result.
Although the catheter can be easily inserted when using the subclavian vein as an insertion route, a smooth pass of the catheter at a branch portion of the blood vessel is difficult, which may result in the catheter being inadvertently positioned in the jugular vein, and in serious complications, such as pneumothorax, hemothorax, hydrothorax, hydromediastinosis or myocardial puncture. Insertion routes, such as via the cephalic vein or the median cubital vein, may result in less serious complications. However, because these routes require a special long catheter, and result in a high incidence of infection or complication of phlebitis, they are not favored.
Accordingly, in general, the external jugular vein is favorably adopted as an insertion route because it is easy to insert the catheter and operate it during insertion, the external jugular vein is the only site by which the central vein may be reached under visual observation, and complications rarely occur because this site is comparatively distant from other major organs.
Conventionally, when the above mentioned external jugular vein as is used as the insertion route, a catheter-assembly is used in the form of a guide wire inserted into the catheter, where the guide wire has less flexibility than the catheter. Thus, the catheter-assembly is inserted over a needle previously inserted into the blood vessel, and the catheter is guided into the intended position with the guide wire. After insertion, guide wire is withdrawn.
However, because the distal end portion of the guide wire in the conventional catheter assembly is straight, it is difficult to make the distal end portion of the catheter enter in the subclavian vein at the corresponding branched portion of the blood vessel, where the external jugular vein joins with the subclavian vein at an acute angle and the catheter must zigzag through a vein valve.
Further, insertion of the distal end portion of the catheter into the central vein is both difficult for the operator, and painful to the patient.